Unlocking the Mysteries of Mars' Past

Since its arrival on the Martian surface in November 2018, the InSight lander was tasked with examining the planet's vital signs—its pulse, temperature, and seismic activity. Equipped with a state-of-the-art seismometer, InSight measured 'marsquakes,' seismic waves resulting from geological activity or meteorite impacts. Although InSight completed its primary mission in 2022, scientists are still analyzing the wealth of data it gathered during its four-year mission.

Cataclysmic Impacts that Shaped Mars

Recent revelations from an international team of researchers, led by Dr. Constantinos Charalambous from Imperial College London, suggest that Mars experienced a series of colossal impacts around 4.5 billion years ago. This claim is supported by seismic evidence indicating the presence of debris fragments from these ancient collisions beneath the Martian surface.

The immense energy generated by these impacts likely melted much of Mars' early crust and mantle, resulting in vast oceans of magma. This suggests that, much like Earth, Mars' geological history was significantly influenced by these violent encounters.

A Unique International Collaboration

Charalambous and his team collaborated with researchers from esteemed institutions such as the Institut de Physique du Globe de Paris, Johns Hopkins University, and NASA's Jet Propulsion Laboratory. They unveiled their findings in a timely study titled “Seismic evidence for a highly heterogeneous martian mantle,” published on August 28 in the journal Science.

Mars' Ancient Mantle: A Geological Time Capsule

InSight’s installation of the Seismic Experiment for Interior Structure (SEIS) in 2018 marked a historic moment as it recorded a staggering 1,319 marsquakes, illuminating the size and composition of Mars' crust and mantle. Similar to Earth, early solar system history was rife with collisions, including one theory suggesting primordial Earth was struck by a Mars-sized body, Theia.

While the size of the objects colliding with Mars remains uncertain, the remnants manifest as fragments within the mantle, some reaching up to 4 kilometers (2.5 miles) in diameter. Charalambous noted, 'We've never seen the inside of a planet in such fine detail and clarity before. These ancient fragments provide insights into Mars' slow evolutionary path, highlighting that Mars hasn't undergone the geological upheavals that have erased similar features on Earth.'

Decoding Seismic Signals

The research team analyzed eight distinct marsquakes whose seismic waves revealed variations within the mantle, indicating materials of different compositions scattered throughout. These findings led to the conclusion that the irregularities likely originated from impacts by large asteroids or planetoids during the early days of the solar system. Co-author Tom Pike of Imperial College London remarked, 'When we examined the quake data, we initially assumed the slowdowns occurred in the Martian crust, but further investigation showed that these delays occurred deeper within the mantle.'

Implications Beyond Mars

This new understanding extends beyond Mars; it paves the way for similar discoveries beneath other rocky planets like Mercury and Venus, which also lack plate tectonics and thus retain evidence of ancient impacts. The revelations from InSight’s data underscore just how much there still is to learn about our enigmatic neighbor.